Compression test will prove rings, valve seats and head gasket. It would be a good start and is easy to do for a garage.

Leaks leading to unburned oil or fuel in the exhaust will destroy your CATs and your O2 sensors if not sorted.

Any startup problems with the HPFP will just lead to excess cranking as the ECU won't open any injectors or fire any ignition until fuel is up to pressure and ready to go. So it may give more cold 'cranks' for oil to be drawn in from any leak before firing thus giving a larger 'puff', if that makes sense?

I agree, when cold, oil in the turbos would't 'puff' blue smoke on start up. It needs to be oil in the combustion chamber for that to happen.

When not running, so you get a start up 'puff', excess oil can only get in the combustion chamber in 3 'gravity assisted' ways:

a) leaking head gasket between oilway and combustion chamber
b) leaking valve stem seal allowing oil to run down a stem from the cam chamber above (past open valve, or pooling on a shut one)
c) oil in inlet manifold running in past open inlet valves, or pooling behind shut valves and being drawn in on start up.

If its a) then this works both ways and will pressurise the oilways/crankcase with combustion gases when running, exacerbating any problems with the PCV, or it will suck oil in to the chamber when on overrun (throttle closed). Has anyone followed you to see if it smokes constantly on overrun, or gives a big puff when you get back on the throttle after overrun?, I suspect it will, as to lose as much oil as you are it can't just be start ups. I also think it will not smoke under acceleration.

If its b) then again it will also smoke on overrun or when re-applying throttle.

If its c) unlikely as you've change the cam cover and integrated PCV cyclonic filters.

BTW mine never uses any oil ever. It's never gone down from 'full' between any oil change (6-8K changes, so i've never put any top-up in it in 40K.

Compression test will prove rings, valve seats and head gasket. It would be a good start and is easy to do for a garage.

Leaks leading to unburned oil or fuel in the exhaust will destroy your CATs and your O2 sensors if not sorted.

Any startup problems with the HPFP will just lead to excess cranking as the ECU won't open any injectors or fire any ignition until fuel is up to pressure and ready to go. So it may give more cold 'cranks' for oil to be drawn in from any leak before firing thus giving a larger 'puff', if that makes sense?

I agree, when cold, oil in the turbos would't 'puff' blue smoke on start up. It needs to be oil in the combustion chamber for that to happen.

When not running, so you get a start up 'puff', excess oil can only get in the combustion chamber in 3 'gravity assisted' ways:

a) leaking head gasket between oilway and combustion chamber
b) leaking valve stem seal allowing oil to run down a stem from the cam chamber above (past open valve, or pooling on a shut one)
c) oil in inlet manifold running in past open inlet valves, or pooling behind shut valves and being drawn in on start up.

If its a) then this works both ways and will pressurise the oilways/crankcase with combustion gases when running, exacerbating any problems with the PCV, or it will suck oil in to the chamber when on overrun (throttle closed). Has anyone followed you to see if it smokes constantly on overrun, or gives a big puff when you get back on the throttle after overrun?, I suspect it will, as to lose as much oil as you are it can't just be start ups. I also think it will not smoke under acceleration.

If its b) then again it will also smoke on overrun or when re-applying throttle.

If its c) unlikely as you've change the cam cover and integrated PCV cyclonic filters.

BTW mine never uses any oil ever. It's never gone down from 'full' between any oil change (6-8K changes, so i've never put any top-up in it in 40K.

Mike, thanks for the detailed input!!

Firstly, i can rule out any fuel related issues including the HPFP as it starts instanly on the button, iíve also had all injectors inpected and changed within the last 8 months. (All injectors are the latest 9th edition part numbers) Second to that the plugs weíre inspected at the wíend and all looked healthy, no carbon build up etc

Point a) Its definatley not a head gasket issue as it was replaced when they did the head, I donít use any coolant and donít get any hot oil smell when up to temp to suggest and external leaking head gasket.

Point c) As you say, unlikley as I had the whole cvankcase cover which contains the PCV check valves replaced recently.

This can only leave one possibility and thats the valve stem seals!! Having spent £1000ís on the head re-build i just canít accept this as somthing iím happy to live with. Iím going to have to speak to Woodís and have the uncomfortable conversation of how we rectifiy the situ, hopfully they can do some tests (compression or whatever) to confirm what is at fault and then we can look athow much of a job it is to correct.

If it is the seals, does anyone know how big a job this is? Are we talking similar to a head gasket change engine out kinda job or smaller?

A head gasket can leak in many different ways, maybe just oil, or just water, or oil to water, some internal only some external only.

So you could have a small leak from an oil way to a cylinder bore without any water issues or any visible signs on the outside.

A compression test would verify integrity of the rings, head gasket and the valve SEATS, but not the valve oil seals.

Valve oil seals are on top of the valve stem, under the valve spring ontop of the head. Not sure of the N54, but it may be a cam out job at most, problem is finding which one of them is at fault!

Do some drive tests with someone following to find out when it smokes, we know Woods are top blokes, so if it is a problem with your recent head work, we know it will be a) an honest failure and b) as gutting to them as it is to you.

Keeps my wallet busy too, if it wasn't such a great car I'd ave ditched it a long time ago believe!!

I'm going to speak to them and start with a compression test which if proves healthy will then single out the seals as the cause.

For the record, I'm one of the biggest advocates of Woods on here!! They've looked after me and have become good mates over the years which is probably why I'm so recurrent to have to address this with them. Any part can fail at anytime regardless and I'm sure usual they'll bend over backwards to rectify the situation.

as an aside, my car was identified as having new injectors fitted under recall, by previous owners. except they were not coded to the car. I had a stench of fuel every now and again, these have now been re-fitted and re-coded the smell has disappeared, blue smoke on crank/fire remains.

H, did you have your head stripped and cleaned (valve seats also) to remove carbon build up?

My thinking is for a puff on cold start, it has to come from the combustion chamber as everything else is too cold to burn oil.

as an aside, my car was identified as having new injectors fitted under recall, by previous owners. except they were not coded to the car. I had a stench of fuel every now and again, these have now been re-fitted and re-coded the smell has disappeared, blue smoke on crank/fire remains.

H, did you have your head stripped and cleaned (valve seats also) to remove carbon build up?

My thinking is for a puff on cold start, it has to come from the combustion chamber as everything else is too cold to burn oil.

Had a full head re-build and complete de-carb, the issue i have is definatley coming from the combustion camber as its imeediate on start up and then clears pretty much instantly.

In general, most oil entry into the combustion chamber will be much increased when on overrun, i.e. slowing on a closed throttle, or mid gearshift, as the vacuum in the chamber during the intake cycle 'sucks' in oil from week points.

When idling or accelerating the combustion gases will do the opposite and prevent oil entry.

Thats why its a good idea to get someone to follow you and, by phone, tell you when they see smoke i.e all the time, on accel, or decel etc.

Bigger fish to fry at the mo as turbo's need replacing. I'm pretty sure its the valve stem seals as its just a brief puff of smoke and is only on cold start and clears instantly, not using excessive oil!!

Hopefully adjustment, but asked them to get some replacements in on a sale or return basis. Given the distance for me to get there and the work involved in getting the downpipes off etc I'd prefer they just fix the car and I swallow the cost if necessary.

my car has been in twice to blue bells, who claim they cannot find anything at all wrong and that the head tech says that "most of them do that" my arguement in that they wouldnt do it from new doesnt seem to wash

to add to this, my oil has dropped 2 bars on the idrive display since mid-october, could be the cold weather, could be continual short journeys (commute is 16 miles a day)

I bet it was the guides. Probably best to do both seals and guides at the same time.

Quote:

Originally Posted by 335i E92

Afternoon

Had a couple of leaking injectors replaced recently, one of the symptoms was a puff of black smoke on start up.

However, now the injectors have been replaced Iím left with a puff of blue / white smoke on cold start up. This only happens after the cars been sat for 7-8 hours plus and clears instantly, seems the black smoke from un burnt fuel was masking something more sinister.

It's only been 7 months since the head was rebuilt and the valve seals we're replaced as part of the re-con, all done by Darren Wood so i'm 100% confident itís not that.

What are the other possibilities, turbo seals? The car runs great and Iím only getting the smoke for a split second on start up. If it was turbo seals would I not have more smoke, like on idle etc? Iím 80k FBOís on stock turboís so itís feasible that they might be on their way out!!